<table class="fixed" border="0">
    <col width="1000px" />
    <col width="500px" />
    <tr>
        <td>
            <h2>ESP32 File Server</h2>
        </td>
        <td>
            <table border="0">
                <tr>
                    <td>
                        <label for="newfile">Upload a file</label>
                    </td>
                    <td colspan="2">
                        <input id="newfile" type="file" onchange="setpath()" style="width:100%;">
                    </td>
                </tr>
                <tr>
                    <td>
                        <label for="filepath">Set path on server</label>
                    </td>
                    <td>
                        <input id="filepath" type="text" style="width:100%;">
                    </td>
                    <td>
                        <button id="upload" type="button" onclick="upload()">Upload</button>
                    </td>
                </tr>
            </table>
        </td>
    </tr>
</table>
<script>
    function setpath() {
        var default_path = document.getElementById("newfile").files[0].name;
        document.getElementById("filepath").value = default_path;
    }
    function upload() {
        var filePath = document.getElementById("filepath").value;
        var upload_path = "/upload/" + filePath;
        var fileInput = document.getElementById("newfile").files;

        /* Max size of an individual file. Make sure this
         * value is same as that set in file_server.c */
        var MAX_FILE_SIZE = 200 * 1024;
        var MAX_FILE_SIZE_STR = "200KB";

        if (fileInput.length == 0) {
            alert("No file selected!");
        }
        else if (filePath.length == 0) {
            alert("File path on server is not set!");
        }
        else if (filePath.indexOf(' ') >= 0) {
            alert("File path on server cannot have spaces!");
        }
        else if (filePath[filePath.length - 1] == '/') {
            alert("File name not specified after path!");
        }
        else if (fileInput[0].size > 200 * 1024) {
            alert("File size must be less than 200KB!");
        }
        else {
            document.getElementById("newfile").disabled = true;
            document.getElementById("filepath").disabled = true;
            document.getElementById("upload").disabled = true;

            var file = fileInput[0];
            var xhttp = new XMLHttpRequest();
            xhttp.onreadystatechange = function () 
            {
                if (xhttp.readyState == 4) 
                {
                    if (xhttp.status == 200)
                    {
                        document.open();
                        document.write(xhttp.responseText);
                        document.close();
                    }
                    else if (xhttp.status == 0) 
                    {
                        alert("Server closed the connection abruptly!");
                        location.reload()
                    }
                    else 
                    {
                        alert(xhttp.status + " Error!\n" + xhttp.responseText);
                        location.reload()
                    }
                }
            };
            xhttp.open("POST", upload_path, true);
            xhttp.send(file);
        }
    }
</script>